Your Fitness Tracker's Calories Burned Metric Is Probably Wrong

Updated: July 6th, 2016

If there weren't already enough studies showing the inaccuracy of wrist worn fitness trackers, there's now a new one. Previously, wrist worn fitness trackers were cited for inaccurately calculating steps and heart rate. So now it's no surprise that researchers out of the University of Queensland in Australia found that these trackers also undervalue exercise levels by 40%.

The study called for 22 participants, both male and female. The wrist worn fitness trackers were provided accurate stats of each individual's height, age, and weight. Participants were tasked to complete varying cardiovascular activities like cycling and running, as well as resting activities like sitting. The wrist band's calories burned data was compared to electrocardiography analysis and a portable gas analysis system. An electrocardiogram, or most commonly known as an EKG machine shows the heart's electrical activity as line tracings on a piece of paper. The varying activity level of the heart is shown in tracings of spikes and dips. A portable gas analysis system is a small machine held in the participants mouth that measures oxygen levels during activity. Compared to these more accurate methods of measuring the body's energy expenditure, wrist worn fitness trackers calculated 40% fewer calories.

Wrist worn tracker's sensors read your blood flow far away from the source, your heart. Many times these sensors that read blood flow are also impacted by light leakage. While other sensors like in the Apple Watch aren't capable of accurately passing light through dark skin. The most accurate method of tracking calories burned and heart rate remains the chest strap monitor watch method, like in Polar Watches. Because chest straps are closer to the heart, they provide a near perfect level of accuracy in gauging heart rate and calories burned.

Popular wrist worn fitness trackers include Fitbit, Tom Tom, and Apple Watch. While the most popular chest strap heart rate tracker brand is Polar, followed by Garmin. While the chest strap can be cumbersome at times to wear, you're only wearing it for a short duration of time.

Your motivation for choosing a more accurate fitness tracker depends on your goals. A fitness tracker should be a tool that you can rely on to help you along your fitness journey by providing accurate information. An accurate fitness tracker will tell you the intensity of your workout, and the calories burned data will help you determine your proper calorie intake for your fitness goals. With chest strap fitness trackers you get the accuracy, and with wrist worn trackers you get comfort. Ultimately the choice is up to you, and which device you feel will benefit you more in your fitness journey.

Which fitness tracker did you choose? Chest strap or wrist worn? What was the deciding factor for you?

*Edited to include source study: http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0154420